Bacteria of various genera are ubiquitously present and grow luxuriantly in organic substrates such as foodstuffs. To determine the level of such organisms, aqueous infusions of foodstuffs such as processed meat and grain are prepared and aliquots of serial dilutions thereof are subjected to conventional plating and culture techniques. Bacterial colonies appear upon the agar surface of ordinary Petrie plates and are counted. This method, however, requires a 24 to 48 hour incubation period, which is too long a delay for commercial production.
A method for eliminating the long incubation period, utilized for testing soil samples and for medical diagnoses, is the fluorescent antibody technique. Where samples for testing are relatively free of other organic matter, the procedure requires merely the incubation of fixed cells with a solution containing specific serum antibody conjugated to a dye molecule which fluoresces at a specific wave length of ultraviolet light. Bacteria so stained are easily visible under an ordinary dark field microscope.
For analysis of complex organic matter, the techniques for immunofluorescence are complicated and require expensive equipment including a microscope designed for epifluorescent visualization. To the knowledge of applicants, no apparatus has heretofore been used or suggested which so simplifies this technique as to make it practicable and inexpensive for routine use in food testing and other industrial applications.